1 - CISAS

1°Symposium On
Space Educational Activities
Space Engineering and Small Satellites Educational
Activities at University of Bologna
Dario Modenini, Marco Bosco, Alfredo Locarini, Paolo Tortora
[email protected], [email protected], [email protected], [email protected]
University of Bologna, Department of Industrial Engineering
Via Fontanelle 40, 47121 Forli, Italy
Padua, 9 – 12 December 2015
Overview
• Department of Industrial Engineering at University of Bologna.
• History & Background: ALMASat-1 mission.
• The European Student Earth Orbiter (ESEO) project.
• Current activities: Missions & Space Technologies
– Micropropulsion
– GPS-Based Navigation
– Ground Segment
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DIN – Department of Industrial Engineering
DIN offers courses in:
• Aerospace Engineering
• Mechanical Engineering
In Forlì
Bachelor and Master’s Degrees
Space-related exams:
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•
•
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Fondamenti di Meccanica Orbitale
Satelliti e Missioni Spaziali
Spacecraft Orbital Dynamics and Control
Spacecraft Attitude Dynamics and Control
Spacecraft Subsystems and Space Mission
Design
Microsatellite and Space Microsystems Lab
Radio Science and Planetary Exploration Lab
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Microsatellite Platforms Heritage @ UNIBO
ALMASat-1
Launched in 2012
Vega Maiden Flight
ALMASat-EO
Launch TBD
ESEO
Launch 2017 (TBC)
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Microsatellites and Space Microsystems
ALMASat-1 (ALma MAter Satellite)
•
•
•
Technology Demonstrator
Micropropulsion Experiment
Transmission Experiment at S-band (2.4 GHz)
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UNIBO students in SPACE
ALMASat-1 microsatellite was entirely
designed, manufactured and assembled in the
Microsatellites and Space Microsystems Lab
of the University of Bologna in Forlì.
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European Student Earth Orbiter (ESEO)
ESEO is a micro-satellite mission of
the European Space Agency (ESA)
Education office.
ESEO will be launched into SS LEO
in 2017 (TBC) and will orbit the
Earth taking pictures, measuring
radiation levels and testing
technologies for future education
satellite missions.
SITAEL (formerly ALMASpace) is the
prime contractor for the platform whilst
UniBO is responsible for the on-board GPS
receiver, TMTC primary GS and MCC.
After successfully passing the PDR and
CDR, the project is now in phase D.
Mass
50 Kg
Altitude
523 km
LTAN
10:30
Attitude
Nadir pointing
Dimension
33x33x63 cm
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ESEO Educational Activities
•
•
•
Lectures, Training Courses and
Internship opportunities were
organised and conducted at system
level at the UniBO and System Prime
premises for 60 students selected
from University Network.
About 200 students are
collaborating to ESEO at different
levels of involvement, most of them
from the premises of all university
teams involved in the project.
In January 2015 the last group of
ESEO students joined UniBO and
SITAEL for their internship period.
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Current SmallSat Activities @ UNIBO
• Following the re-organization of its industrial branch (ALMASpace), the
Microsatellites and Space Microsystems Lab at University of Bologna is now
focusing on the following target areas:
– Micropropulsion systems
• Cold-gas (Nitrogen):
– Flown on ALMASat-1 in 2012 (not tested)
– To be flown under a different system configuration
on ESEO (developed by SITAEL with UniBo support)
• Monopropellant (warm-gas), under development, jointly with SITAEL and FBK
– GPS Receivers and Autonomous Navigation Systems
• To be flown on ESEO, as part of the payload package,
in collaboration with SITAEL
– Ground Segment/Station Technologies and Mission Control Centers
• UNIBO is responsible for the ESEO Ground Segment
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Missions & Space
Technologies
A) Micropropulsion
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ALMASat-1 Cold-Gas µprop system
• Gaseous Nitrogen Propellant, pressurized in a
tank, flowing through a De-Laval nozzle
• MEMS-based micronozzles
(L throat = 40μm) with thrust ≈ 1 mN
• Applications: attitude and orbit control
• Same concept re-adapted for ESEO mission
Microscope image of the nozzle throat area
(courtesy of CNR Bologna)
• Pros: simple fluidic layout, possibility to set target
thrust at extremely low levels
ALMASat-1 Cold gas μ-propulsion system
• Cons: Low specific impulse (≈ 60 s) and limited
total impulse (attainable ∆V) due to low storage
density
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Monopropellant (Warm-Gas) µprop system
• Under development under joint collaboration with
SITAEL and FBK
• Based on exothermic catalytic decomposition of
H2O2  ½ O2 + H2O (green!)
• High concentration H2O2 propellant produced in-lab
• MEMS-based device, integrating a catalytic
chamber and a micronozzle in a single unit
Monopropellant system working principle
• Advantages wrt Cold-Gas: High Specific Impulse (≈
150 s), propellant with high density storage
(lower storage volume)
MEMS-based microthruster prototype
manufactured at FBK premises
• Disadvantages: more complex system (management
of the liquid propellant, possible pre-heating of the
device, ignition time)
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H2O2 µ-thrusters prototype testing
•
•
A first batch of prototypes were tested with
in-lab distilled H2O2, injected through a
syringe pump
Only an incomplete propellant dissociation
was achieved in the chamber:
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•
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A bubbly gas-liquid mixture is found at the
nozzle rather than the expected warm gas
stream
Preliminary Thruster sizing geometric
parameter and target performance
Throat Sizer: Dt
40 μm
Constant Height: H
320 μm
H O initial concentration: %
87.5 %
H OAdiabatic Temperature: T
949 K
≈ 1 mg/s
Mass flow rate: �
Thrust: F
≈ 2 mN
Specific Impulse: Isp
150 s
2
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SEM pictures of samples sections showed
that catalyst deposition was not uniform all
over the device.
Indications of the need for:
a) improved catalyst deposition process, and
b) deeper insight into complex interactions
within the reacting multiphase flow.
End of the decomposition chamber and nozzle
convergent region showing the “bubbly flow “ operation
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Missions & Space
Technologies
B) GPS-Based Navigation
system for satellite missions
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ESEO GPS Payload
MISSION TARGETS
•
•
To verify in space environment the functionality of
commercial technologies, commonly used in
terrestrial GNSS receivers
To develop and test of a sophisticated navigation
algorithm, in order to determine the positioning
accuracy achievable by a commercial receiver on
board of a satellite.
NAVIGATION FILTER DESIGN
Two different algorithms will be hosted on board of the payload:
•
Kinematic solution: a direct computation of the receiver position from the raw observables, without filtering it
by an orbit dynamic model. The provided accuracy is the typical accuracy of ground application, between 10-15
m 3D RMS. The method used to determine the position is based on Least Square Algorithm.
•
Reduced dynamic solution: this algorithm is based on the integration of the raw observations within an
accurate orbit dynamics model, using an Extended Kalman Filter. According to the complexity of the model
and to the observation combination, this algorithm 3D RMS accuracy is between 60 and 80 centimeters.
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Functional Architecture
A passive antenna from Sensor Systems with flight heritage,
model S67-1575-20, mounted on the satellite top panel.
Custom PCB designed to provide the correct
interface between the passive antenna and
the based-band processors.
A custom on board computer that
hosts the navigation filter and
manages the power for the entire
payload and antenna. It also collects
positioning data and distributes them
to the other subsystems.
Two OEM615 receiver, from
Novatel, in cold double redundancy,
that performs GPS signal acquisition,
tracking and data demodulation. It
provides the raw GPS measurements
together with the GPS satellite
broadcasted navigation data that is
required to compute the navigation
solution.
COCOM
limitations
removed.
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Test and Verifications
Recursive Filter test: in order
to verify the performance of
the navigation algorithm in a
real
scenario,
it
was
implemented and used to
process
GRACEA
raw
observations.
Results:
The
off-line
processing
showed
a
positioning error of about
80cm 3D RMS when using
broadcasted GPS ephemeris
and clocks. It is expected that
the ESEO positioning error
will be worse, between 1 and
1.2 meters, due to the lower
quality of the receiver
oscillator.
Baseband Processor Test: a functional test
was performed at the ESA/ESTEC facilities
using a GPS signal simulator, in order to
ensure that the receiver is suitable for
operations on-board the satellite. Mission
scenario simulated to verify functionality with
typical space doppler values.
Results:
•
need for an initial forced setting of the
receiving channel’s frequency scanner (to
space Doppler values),
•
obtained mission data consistent with the
simulation scenario.
Communication
test:
full
functional test performed on the
payload in “flight configuration”
in order to verify the correct
hardware
and
software
implementation
of
the
communication
between
the
microcontroller of the custom
PCB and the COTS front end.
Thermal test: performed to assess
the functionality of both the COTS
baseband processor and the
custom navigation computer under
external thermal conditions close
the ones experienced in orbit. The
thermal chamber was set first to
-25° and then to 70°, and in both
cases an electrical and a functional
tests have been performed.
Results: no critical degradations
of the performances occurred
under extreme external conditions.
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Missions & Space
Technologies
C) Ground Segment
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ESEO Ground Segment and
Ground Station Network
Serial
ROTOR
Orbit
Propagator
1GB
Ethernet
USRPN210
GNURadio
GS SatNet
Client
Serial
SatNet
Orbitron
ROTOR
1GB
Ethernet
USRPN210
LabVIEW Data
Dashboard App
Internet
UDP
GSM
MUNICH
Web
Services
GNURadio
UDP
ESEO Platform
HSTX
ODBC
Engineering
Data
UDP
JSON-RPC
Over HTTPS
TMTC
Protocol
Serial
AMSAT
Gpredict
ROTOR
MCS Satnet
Client
Engineering
Data
JDBC
Users
Science Data
1GB
Ethernet
USRPN210
SYNC
LabVIEW
GS SatNet
Client
GSF2
DataBase
Server
MCS PC
LabVIEW
UDP
GS SatNet
Client
GSF1
FORLI
University of Bologna
Serial
Orbitron
ROTOR
University of Vigo
Serial
ICOM+TNC
GS SatNet
Client
TU Munchen
GSV VIGO
AMSAT COMMUNITY
WORLDWIDE
SITAEL
University of Wroclaw
Internet
AMSAT-UK
AMSAT Data
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SDR based Ground Station
SDR technology allows students to have hands-on experience on digital
communications and better understand the theoretical principles behind
modulations schemes and communication protocols.
TX:
• Digital to Analog Conversion
• RF Upconversion
RX:
• RF Downconversion
• Analog to Digital Conversion
TX:
• Modulation
• AX.25 encoding
• BB transmission
RX:
• Signal Display (Spectrum, Waterfall, ..)
• Signal Recording
• Demodulation
• AX.25 decoding
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ESEO M&C System
• Connected to the S/C
Database
• TC selection
• TC stack
• TC acknowledgments
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TM packets display
TM data display
On-board schedule display
Automatic e-mail warnings
TM playback
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Satellite Passes and Conflicts Engine
(SPACE)
• Satellite passes over GS
• Conflicts detection and resolution of
passes based on GS priority list.
• Results are displayed as html pages.
• TLE propagators are open-source
Python libraries: pyorbital and pyephem.
• TLE can be retrieved from internet
(CelesTrack) or from local.
• Azimuth dependent horizon mask can be
added as CSV files.
Conflict-free pass schedule
three S/C (y-axis)
over three G/S (legend)
for one day (x-axis)
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Thank you for your attention!
Dario Modenini, PhD
Research Fellow
Micropropulsion
Email: [email protected]
Marco Bosco
PhD student
Ground Segment
Email: [email protected]
Paolo Tortora, PhD
Associate Professor
Alfredo Locarini
PhD student
GPS-Based Navigation
Email: [email protected]
Course Director, BSc and MSc in Aerospace Enginering
Email: [email protected]
University of Bologna,
Department of Industrial Engineering
Via Fontanelle 40, 47121 Forli, Italy
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µProp status and roadmap
•
Cold gas N2 µProp system is reaching a high maturity level, expected in-orbit testing
onboard ESEO S/C.
•
Current efforts focused towards H2O2 monopropellant, encompass several areas:
1. MEMS design and manufacturing
2. Catalytic decomposition kinetic experimental tests
3. Numerical modelling
•
Tests over first batch of prototypes revealed only a partial degree of decomposition calling
for a deeper insight into the catalytic decomposition.
1. Decomposition kinetic studies (currently in advanced state)
2. Full 3D FEM model for the biphase-chemically reacting-evaporating flow around pillars (currently
in advanced state)
3. Manufacturing: improved design and catalyst deposition in a reproducible and controllable way
(under preparation)
•
Next generation of thruster prototypes expected to be ready for testing in the next few
months.
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ESEO GPS Payload
Educational content
Opportunity for students to directly face problems and issues that may rise
during the design of subsystems for real space missions
Training for students in order to conform their work to the quality standards
of ESA missions, thanks to the frequent reviews to which the payload is
subjected.
Technological content
• low-cost solution for GPS positioning in space
• high quality data
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Forli TMTC GS + S/C M&C
SDR PC
MCS PC
RX chain
437 MHz GFSK
Ethernet
Signal
Acquisition
Buffer
Demodulation
AX.25
decoding
UDP
Buffer
Buffer
TM data
Extraction
ODBC
Signal
Recording
TM storing
TX chain
SDR PC
Ethernet
Signal
Transmission
MCS PC
Modulation
UDP
AX.25
encoding
TC data
Manipulation
435.2 MHz GFSK RS
ODBC
ODBC
TC storing
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Mission Control Room and Antennas
• VHF/UHF Yagi antenna (144-146, 430-440
MHz).
• S-band antenna (CCSDS frequency ranges)
• Downlink and uplink operations
• Dedicated mission control room
Students will learn by following and performing
satellite operations.
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